1. Field of the Invention
This invention generally relates to a method and an apparatus for monitoring and controlling noise and, more particularly, to a method and an apparatus for monitoring and controlling exposure to noise related to a headset.
2. Description of Related Art
In a work environment, the accumulated amount of noise, or dose in terms of an average noise level, and the maximum level of noise to which an individual has been exposed during a workday are important to occupational safety and to the health of the individual. Industry and governmental agencies in countries throughout the world, such as the Occupational Safety and Health Administration (OSHA) in the United States, require accurate noise data measurements.
Examples of such noise data measurements include impulse noise, continuous noise, and an eight-hour time-weighted average (xe2x80x9cTWAxe2x80x9d). Impulse noise relates to noise of very short duration, less than a few thousandths of a second, which also repeats less than once a second. Continuous noise relates to noise that is longer in duration than impact noise, extending over seconds, minutes, or hours. Eight-hour TWA relates to the average of all levels of impulse and continuous noise to which an employee is exposed during an eight-hour workday. The OSHA maximum level for impulse noise is 140 dBSPL measured with a fast peak-hold sound level meter (xe2x80x9cdBSPLxe2x80x9d stands for sound pressure level, or a magnitude of pressure disturbance in air, measured in decibels, a logarithmic scale). The maximum level for continuous noise is 115 dBA (read on the slow average xe2x80x9cAxe2x80x9d scale). OSHA regulations limit an eight-hour TWA to 90 dBA. If employees are exposed to eight-hour TWAs between 85 and 90 dBA, OSHA requires employers to initiate a hearing conservation program which includes annual hearing tests.
Among the many noise sources that are encountered in the workplace, measuring the exposure to noise related to telephone headsets is especially problematic. Telephone headsets generate their sound levels at or in the user""s ear canal rather than external to the user. The external sound field levels referred to in many governmental regulations cannot be directly compared to these headset sound levels.
Also, headset users in the workplace typically have jobs requiring either that they spend a substantial amount of time on the phone, or that their hands be free to perform other tasks. Since the headset user""s speaker is held in or against the user""s ear, the user requires more time to respond to any irritating tones or noises by moving the speaker further away from the ear than one typically does with a regular telephone handset. Exposure to impulsive sounds and short duration tones can be capped by protective devices such as forward breakdown diodes. However, there is currently no method to easily measure and control day long exposure from a headset. While telephone signals generally do not approach TWA limits, new sources of signal input are becoming available to users of telephone headsets. For example, headsets used for telephony may also be connected to a computer, allowing access to music sources. Some individuals may listen to music at levels much higher than the voice signals of typical telephone systems. As such, a headset user is exposed to varying levels of sound pressure over varying lengths of time with no capability of assuring real-time compliance with average noise exposure limits set by OSHA or other governmental regulations. Previously, remedial measures have generally been implemented after exposure to excessive noise and thus, there has been no prior method or apparatus to assure real-time compliance with threshold limits.
Therefore, there is a need in the art for a headset audio dosimeter that monitors the aforementioned data related to noise exposure levels in real time and that also controls the noise exposure to the headset user in real time to comply with governmental regulations and ensure user safety.
In accordance with the present invention, a method and an apparatus are provided for monitoring and controlling exposure to noise related to a headset apparatus. A method for monitoring audio dosage from a headset includes sampling an input sound signal, calculating a headset sound level based on the input sound signal samples, and calculating the cumulative exposure of the headset user to the headset sound level at a specific point in time. These calculations are repeated to update the measure of the user""s cumulative exposure to sound during the time that the user is wearing the headset. Advantageously, the present invention accurately monitors in real time audio dosage related to a headset apparatus.
In another aspect of the invention, a method for controlling audio dosage from a headset includes sampling an input sound signal, calculating a headset sound level from the sound signal samples, calculating real-time exposure to the headset sound level, extrapolating exposure to the end of a time period, calculating a gain adjustment for the input sound signal, and adjusting the gain of the headset to control the amplitude of the input sound signal. Advantageously, the present invention allows real-time compliance with regulatory threshold levels for exposure to noise. In addition, the invention may incorporate the ability to restrict impulse noise and short term tones to levels below regulatory limits.
In another aspect of the invention, a headset audio dosimeter includes a sampler means, a technique for calculating a headset sound level, a technique for calculating real-time exposure to the headset sound level, and a technique for calculating a gain adjustment to apply to the input sound signal.
In yet another aspect of the invention, a headset audio dosimeter system for processing an input sound signal from a source includes a sampler, a processor, a memory, a program with instructions stored in the memory that calculates not only a headset sound level but also real-time exposure to the headset sound level and a gain adjustment for the headset, gain adjust circuitry for adjusting the gain of the headset in response to the gain adjustment output by the program, and a headset apparatus.
Advantageously, the present invention accurately monitors cumulative dosage to sound related to a headset apparatus and calculates periodic gain adjustments, if necessary, to remain in compliance with regulatory threshold levels for exposure to noise.
These and other features and advantages of the present invention will be more readily apparent from the detailed description of the embodiments set forth below taken in conjunction with the accompanying drawings.